I ran your batch file through the debugger in both v16 and v17, and there is a difference (and a bug) between the two versions. However, the bug is in v16 (actually in the RTL), not in v17 (which is using an updated RTL).
I made a change to build 59 (already uploaded) which should resolve your issue, though it does break compatibility with CMD.
I do have two questions:
1) Why are you using ParameterChar? It has been obsolete for at least 12 years; it was added many years ago to ease transition between 4DOS and 4NT batch files, and changing it now only makes your batch files incompatible with everybody else (and vice versa).
2) Why did you choose that particular character? It's one of a handful in that character set that don't translate between code pages. (Each code page and font combination have between 0 and 10 characters that are mangled by Windows during translation to & from Unicode; your 0xF8 is one of them.)